In most trenching operations in which the depth of the trench is at least five feet, safety measures must be taken to protect the worker within the trench. Section 29 of the Code of Federal Regulations (at Part 1926, Subpart P) specifies that, under certain conditions, protective structures, such as trench shields, may be used in such trenches.
The trench shields provided by the prior art, however, are relatively expensive and cumbersome and, thus, are especially unsuitable for applications in which one worker needs to work on a long trenched section.
By way of illustration, a self-propelled trench shield is disclosed in United States patent of Seyle. The device of this Seyle patent is suitable for a situation in which it is required to simultaneously dig a trench and move the device. However, in situations in which a trench already has been dug and it is desirable to perform some secondary operation (such as, for example, cleaning the trench or laying pipe), the Seyle device would not be suitable and could not be self-propelled along the already-dug trench.
By way of further illustration, a rather large trench box is disclosed in U.S. Pat. No. 4,850,747 of Morelli. Because of the size of the trench box of this patent, it must be moved down the trench by a machine and, thus, is not suitable for operation by only one worker.
By way of further illustration, a self-propelled trench shoring machine is disclosed in U.S. Pat. No. 4,874,271 of Arnold. The device of this patent is rather large, complicated, and thus expensive. It does not appear to be suitable for use in irregularly shaped trenches; and it probably would require either several workers and/or a machine to place it into a trench.
It is an object of this invention to provide a trench shield which is relatively inexpensive to manufacture and use.
It is another object of this invention to provide a trench shield which can readily be moved within a trench by only one worker.
It is another object of this invention to provide a trench shield which can readily be moved within irregularly shaped trenches.
It is yet another object of this invention to provide a trench shield which is comprised of means for fixedly setting the shield in a desired position within the trench.
It is another object of this invention to provide a trench shield which does not substantially impede the vision of a worker disposed within such shield.
It is yet another object of this invention to provide a trench shield which is relatively lightweight.